1. Field of the Invention
The present invention is directed to a variable volume gas generator.
2. Description of the Prior Art
There are two main categories of motors among heat engines, which transform the thermal energy provided by fuel into mechanical energy, continuous flow motors of the gas turbine type, which operate according to the Joule cycle, and volumetric motors wherein compression and expansion are obtained by volume variation and which operate according to the Beau de Rochas (gasoline engines) or Diesel cycle.
None of the motors which fall within these two categories is completely satisfactory insofar as the continuous flow motors have an advantage over the others in that they are lighter, which makes them preferable for use as aircraft engines, but their specific fuel consumption is high, on the order of 200 g per horsepower hour for large gas turbines, a figure which can increase to 300 or more for small gas turbines. Correspondingly, gas and Diesel volumetric motors are heavy and bulky, which is a serious disadvantage but is, in general, acceptable for terrestrial motors because of their low specific fuel consumption (Diesel motors may have specific fuel consumption levels on the order of 150 g per horsepower hour).
The differences in specific fuel consumption between continuous flow and volumetric motors expressed above are based on optimum operating conditions at constant load for both types of machines. These differences are even greater when the motors are operating under a partial load, wherein the specific fuel consumption of continuous flow engines increases rapidly when the load is reduced while, on the contrary, the specific fuel consumption of Diesel engines varies only slightly and may even improve when the load is reduced.
As compared to conventional piston engines, rotary volumetric motors provide a substantial reduction of bulk and mass while retaining the excellent yield provided by the piston engine, and this for the reasons disclosed in French Patent application No. 2,475,126.
This patent application in particular describes rotary volumetric motors including a fixed housing delimiting an annular chamber in which pistons which rotate in the same direction are mounted, such pistons being diametrically connected in pairs by a rod and additionally propelled by a cyclical speed variation causing a volume variation in the space delimited by the radial surfaces of the pistons, and wherein such spaces between the pistons form the chambers of a motor operating on a four stroke cycle.
The annular space in which the piston moves is delimited by the housing and a rotary crown having ports through which the rods are engaged and which provide an angular clearance for the rods enabling the pistons to advance and to recede, such crown forming the engine outlet shaft or being connected to it and being connected by a transmission mechanism to the shafts which are an integral part of the piston rods. However, at high power, for instance at a power greater than 500 hp, this four cycle motor could be advantageously used as a gas generator to be used to charge a self-contained turbine from which the motor effort is taken.